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March 20, 1962 P. M. MCPHERSON 3,026,435 ULTRAVIOLET LAMP Filed Sept. 16, 1960 5 Sheets-Sheet 1 B AT TORNEYS 4 March 20, 1962 3,026,435 P. M. MCPHERSON ULTRAVIOLET LAMP Filed sept. 16, 1960 5 Sheets-Sheet 2 -4--2 à l 7c? l; I I l l l l l | j p l l i î l l | ‘ i i l 3 l . 45~»' " = ‘l --- 74 52 34” » ß \\l . i l@ __ l @_ k‘ /75 __ î/’PÚ f/ 66 ‘56 Y F I G. 2 -<`.¢?f_5_ INVENTOR. Y @mmm BQZQWSL/Mwq _ ATTORNEYS ' March 20, 1962 P. M. McPHl-:RSON ULTRAVIOLET LAMP Filed Sept. 16, 1960 3,026,435 „ 5 Sheets-Sheet 3 GAS INLET 56 ¿ATTORNEYS March zo, 1962 ` P. MMCPHERSON 3,026,435 ULTRAVIOLET LAMP Filed sept. 16, 1960 5 sheets-sheet 4 ATTORNEYS March 20, 1962 P. M. MCPHERSON 3,026,435 ULTRAVIOLET LAMP Filed Sept. 1G, 1960 ' 5 Sheets-Sheet 5 INVENTOR. BY ATTORNEYS , ‘United States arent f vfice SßZbALÈS Patented Mar. 20, 1962 1 2 3,026,435 ot the present invention, reference should be had to the following detailed description taken in connection with UL'I'RAVIOLET LAX/IP Pani M. McPherson, Acton, Mass., assigner to McPher the accompanying drawings wherein: spn Instrument Corporation, Acton, Mass., a corpora FIG. 1 is a top plan view, partly broken away, of a vacuum ultraviolet lamp embodying the present inven Filed Sept. 16, 1960, Ser. No. 55,466 12 Claims. (Cl. 313-22) tion, shown in conjunction with a fragment of a spec tion of Massachusetts trometer; FIG. 2 is a vertical cross-sectional view, partly bro The present invention relates to the generation of ultra ken away, of the lamp of FIG. l, the section being taken violet radiation and, more particularly, to a high power 10 substantially along the line 2--2 of FIG. 1; ultraviolet lamp for use in conjunction with spectro FIG. 3 is a cross-sectional view, partly broken away, scopic apparatus. of the lamp of FIG. 1, the section being taken substan That part of the electromagnetic spectrum having wavelengths shorter than 2,000 A. is frequently called the vacuum ultraviolet region because the high absorp tion of such wavelengths by most gases often requires the evacuation of spectroscopic apparatus utilizing such the section being taken substantially along the line 4-4 wavelengths. Thus, a typical spectrograph for use in this region comprises an entrance slit through which ultraviolet radiation is transmitted from a source, a dif section view of a part of the lamp of FIG. l; and FIG. 6 is a perspective, disassembled View of the lamp of FiG. 1. fraction grating for dispersing this radiation from the Generally the illustrated embodiment of the present invention, with reference to FIGS. l, 2 and 6, comprises entrance slit into a spectrum, an exit slit for transmitting a selected part of this spectrum from the dittraction grat ing to desired auxiliary apparatus and means for evacu vating the diffraction grating chamber. tially along the line 3-«3 of FIG. l; FIG. 4 is a cross-sectional view of the lamp of FIG. l, of FIG. 1; FIG. 5 is an enlarged, fragmentary, partially crossed a source 20 of ultraviolet light in conjunction with a spectrograph 22 that includes: an entrance slit 24 The lamp for 25 through which ultraviolet radiation from lamp 20 enters; a diffraction grating (not shown) of conventional design such a spectrograph generates ultraviolet radiation by applying a high potential across an ionizable gas in a tube that is sufticiently narrow to concentrate the result ing radiation in a narrow beam. In order to maximize that disperses the radiation from the entrance slit into a spectrum; an exit slit (not shown) of conventional de sign through whic'n a selected portion of the spectrum the energy transmitted through the slit from the lamp, 30 is transmitted from the grating; and a Vacuum pump this tube is oriented perpendicularly to the plane of the (not shown) of conventional design for maintaining the slit so that emission of the beam in an axial direction interior of the spectrograph at reduced pressure. The from an end of the tube is eiïected. In the 1000 to 2000 slit is shown in FiG. l at 24 as being provided by a plate A. region, it may be practicable to confine the gas with 25 that is mounted upon a support 28. Support 2S pro in an envelope which eiiîciently transmits ultraviolet 35 vides an aperture 30, through which radiation from slit radiation. However, in the region below 1000 A., high 25 may enter the evacuated interior 32 of the spectro absorption by most solid materials renders the design of graph. a suitable envelope impracticable. Accordingly, it is nee Generally lamp 20 includes an ultraviolet source in the essary in this short wavelength region to transmit energy form of a capillary tube 34 that extends between an _directly from the plasma of the lamp through the slit 40 anode 36 and a cathode 33. Typically, capillary tube of the spectrograph. Furthermore, because of a require 34 ranges from lÁs to 1/2 inch in diameter. Anode 35 men for the generation of ultraviolet radiation of de is provided with a central bore 40, into which snugly sired intensity, high potential difference is necessary projects one end of capillary tube 34. Cathode 38 is across the plasma and great heat is produced in the provided with a central bore 42, into which snugly pro plasma. The present invention contemplates a simpli jects the other end of capillary tube 34. The seals be fled construction of the foregoing type characterized by tween the outer periphery of capillary tube 34 and the eñîcient heat exchange for preventing excessive heating inner periphery of bore 40 and between the outer pe of the lamp, eñective mounting and shielding of com riphery of capillary tube 34 and the inner periphery of ponents to facilitaterhandling and eliminate hazard and bore 42 is ensured by rubber-like O-rings 44 and 46. limited mechanical communication between the evacu Cathode 3S is mounted upon anode 36 by three in 50 ated spectrograph chamber and the pressurized plasma sulating posts 4S, 50 and 52, which electrically isolate tube in order to minimize leakage of plasma from the cathode 3S from anode 36. An ionizable gas, preferably lamp to the spectrograph. a noble gas such as argon or an inert gas such as nitrogen, Objects of the present invention are: to provide a is introduced into the axial capillary oriñce 54 of capil combination of the foregoing type wherein the conduit lary tube 34 through a fitting 55 and a bore 58 in cathode defining the optical path for radiation from the plasma 36 that communicates with bore 40 of cathode 36. Bores 49 and 42 of anode 36 and cathode 33 are designed to trograph in such a Way as to confine mechanical com contain a substantial quantity of this gas. The arrange munication between the spectrograph and the lamp to ment is such that the pressure of the gas within capillary the cross-sectional area of the slit; to provide a lamp orifice 54 is maintained constant by the pressure sinks 60 for an apparatus of the foregoing type in which all com constituted by bores 40 and 42. A suitable pressure con is sealed directly to the face defining the slit of the spec ponents are mounted on a grounded electrode and with trol (not shown) is associated with ñtting 56 in order to in a grounded shroud for facility and safety; and to pro maintain the pressure of the gas within the system con vide a lamp of the foregoing type in which the plasma stant notwithstanding its escape from the system in minute tube, which is composed of an electrical insulator, is 65 quantities through slit 24 in a manner to be described below. mounted between the anode and the cathode, which are Capillary tube 34 is shaped to include a water jacket composed of electrical conductors, in such a Way that the grounded electrode and tube may be Water cooled 60 (FlG. 4), through which water is circulated between an inlet 62 and an outlet 64. Water jacket 60 serves and the “hot” electrode may be air cooled. to maintain capillary tube 34 at a predetermined tem Other objects of the present invention will be obvious 70 perature notwithstanding the heat generated by the plasma y `-»and will in part appear hereinafter. For a fuller understanding of the nature and objects within capillary oriiice 54. This plasma Ialso transfers 3,026,435 3 4 departing from the scope of the present invention, it is intended that all matter >contained in the above descrip tion or shown in the accompanying drawings shall be heat to anode 36 and cathode 38. Anode 36 is provided with an annular bore 66 into which water is fed through a fitting 63 and from which Water is fed through a Íit- , interpreted in an illustrative `¿and not in a limiting sense. ting 7d. Fitting 7G Vcommunicates with inlet 62 of capil lary water jacket 60 Vthrough a tubeV 71 so VthatV both What is claimed is: l. in combination with spectroscopic means including an evacuated chamber, an entrance-¿slit communicating therewith through which ultraviolet radiation may be transmitted, a dispersion means for dispersing (the ra anode 36 and water jacket 60 circulate the same stream of water. Cathode 38, which because of its extremely lowV potential must Vbe _electrically isolated, is provided with a multiplicity of ñns 72 that are air cooled by a suitable motor driven fan 74. Motor driven fan 74 is mounted on a cage 76 of generally cylindrical contigura tion. One end of cage 76 is aiiixed to anode 36 as at 7S andthe other end of cage 76 is closed by a cap 80.v diation from the entrance slit into a spectrum and an exit slit communicating for selectively transmitting: a re stricted portion of said spectrum, an ultraviolet lamp com prising first electrode means providing a seat, Vsecond electrode means providing a seat, spacing means between said second electrode means and said iirst electrode means Cage 76 is articulated in order to permit free ilow of air through iins 72. Anode 36, cage 76 and cap 80 com pletely surround cathode 38 in such a way as to prevent for mechanically connecting and electrically isolating said second electrode means and said'iirst electrode means, a manual contact of cathode 38 when the lamp is in opera tube providing a central oriiice, one extremity of said tion. Anode 36, cage 76 and cap 80 are grounded so tube being received hermetically by said seat of said first that they may be freely handled without danger. As is Vbest shown in FIG. 5, anode 36 abuts against 20 electrode means, the vother extremity of said tube'being received hermetically by the seat of said second electrode a plate ,82, to which it is sealed by concentric O-rings 84 and V86. Plate S72 is provided with an outwardly project means and means for introducing a gas into said cen ing hub 8S. A central bore 9i) extends through hub 88 and plate 82.Y Atrthe center of plate 82 is aiiixed an aperture disk 92. Projecting toward plate 26, which pro vides slit 24, from within bore 90 is a hollow tubelet 94. The outer periphery of tubelet 94. contacts the face of plate 26 and is sealed thereto by means of a suitable O tral oriiice. A' ` e ' 2. ln the combination of claim l, a water jacket sur rounding said tube. ' 3. In the combination of claim 2, said second elect-rode means providing a duct, and a> coolant forcirculation through _said duct and said water jacket. i ` 4. ln the combination of claim 3, a cage enveloping ringV 97. The rearward end portion of tubelet 94 is pro vided with a peripheral slot 95. Projecting into slot 95 30 said iirst electrode means and connected to said second electrode means, said 'second electrode means and said is a ñnger 96 that extends from and is eccentric to a shaft cage _being grounded, said first electrode means being at 98. Shaft 98 is rotatable in a bore 100. By rotating a potential other than ground. Y the knurled head 102, which is attached to the outer end >5. In the combination of claim l, a reciprocable hollow of shaft 98, tinger 96 is caused to bear against slot 95 in such a way as to cam the outer end of tubelet 94 35 sleeve communicating with said bore of said second elec Ytrode means and means for wedging said reciprocable against plate 26. sleeve against said entrance slit of said spectroscopic In operation, fan 74 is energized by such means as a means. Y switch 134. The pressure of the ionizable gas within 6_. In combination with spectroscopic means including bore 40 of anode 36, capillary oriiice 54 and bore 42 of cathode 38 isY built up. Spectrograph cavity 32 is evacu 40 an evacuated chamber, an entrance slit communicating therewithn through which ultraviolet radiation may be ated. Water is ilow through inlet 68 of anode _36, from transmitted, a dispersion means for dispersing the radia outlet 79 to inlet 62, through Water jacket 60 and from tion from theV entrance slit into a spectrum and an exit outlet 64. A-negative potential of from 10,000 to 30,000 slit communicating for selectively transmitting a re volts, and preferably of about 15,00 volts, is applied to cathode 38.` In consequence, a dischargeioccurs through 45 stricted portion ofv said spectrum, an ultraviolet lamp comprising lirst electrode means providing a seat, second the gas within capillary orifice 54 in such a Way that electrode means providing a seat, spacing Vmeans between heavy cations are directed toward cathode 38 thereby said iirst electrode and said second electrode means for rendering the pressure toward cathode end of capillary mechanically connecting and electrically isolating said oritice 54 higher than the pressure at the anode end there of. The slivht leakage of gas through slit _24 into the 50 second electrode means and said ñrst electrode means, a tube providing'a central orifice and a lsurrounding water evacuated chamber 32 of the spectrograph is minimized jacket, said water jacket being composed of an insulat by tubelet 94 which abuts against the face of plate 26. ing material, one extremity of said water jacket being re Typically, the pressure in the spectrograph is maintained ceived hermetically by said seat of said iirst electrode at an order of a few microns of mercury and the pres sure in the lamp is maintained at an order of a few 55 means, the> other end of said water jacket being received hermetically by said seat of said >second electrode means, means for introducing a gas into said central orilice, said second electrode means providing a duct means for circu millimeters of mercury. The present invention thus provides a simply .designed ultraviolet lamp that is capable of directing intense ultra violet radiation directly from a plasma through the slit latingU coolantthrough said ductl and throughV said water window. The intense radiation is made possible by a high potential ditierence across the plasma and an eili Ycient cooling system. All of the components are mounted 7. in the combination of V'claim 6, said first electrode means being at a potential other than ground, and a cage of an evacuated spectrograph without an intermediary 60 jacket, tins on said second electrode means, and'means Vfor blowing air over said tins. " ' ’ enveloping said first electrode means and connected to simply in such `a way as to eliminate danger by virtue said second electrode means, said second electrode means of a grounded cage that completely envelops a low po 65 and said cage being grounded. tential cathode and that is mounted on a grounded anode. In alternative embodiments of the present invention, the polarity of the electrodes are reversed such that elec trode 36 is the cathode at ground and electrode 38 is the S. ' An ultraviolet lamp comprising -tir’st electrode means providing a seat, second electrode means providing- a seat, spacing means between said second electrode means anode at elevated potential or `an alternating current is 70 applied across the electrodes. -In another alternative embodiment of the present invention, the ionizable gas is fed into the system through bore 42 rather than bore 40. Since certain other changes may be made in the above and said iirst electrode means’for mechanically connect ing and electrically isolating said second electrode means ` and said iirst electrodeV means, and a tube providing a central oriiice, one extremity of said tube being received hermetically by said seat of said iirst electrode means, _described embodiment of the present invention without 75 the other extremity of said tube being received hermetical 3,026,435 5 6 ly 'oy said seat of said second electrode means, means for introducing a gas into said central oriñce, said first elec trode means being at a potential other than ground, and therebetween, one of said electrode means providing an opening therethrough communicating with said tube means, means for introducing a gas into said tube means, a cage enveloping said ñrst electrode means and con means for applying a potential between said ?rst electrode nected to said second electrode means, said second elec trode means and said cage being at ground potential. 9. The ultraviolet lamp of claim 8, wherein a water means and said second electrode means, means for mount jacket surrounds said tube. lO. The ultraviolet lamp of claim 9, wherein one of sleeve means remote from said opening, and means for ing a sleeve, means for> reciprocal motion in communica tion with said opening, gasket means at the end of said reciprocating said sleeve means. said electrode means provides aV duct, and a coolant is 10 12. The ultraviolet lamp of cla-im l1 wherein said provided for circulation through said duct and said water gasket means is an O-ring. jacket. l1. An ultraviolet lamp comprising first electrode means, second electrode means and tube means extending No references cited.